In hopes of improving air quality, City Councilor Michael Ross wants to authorize Boston’s parking enforcement officers to issue tickets to drivers violating antiidling laws and City Councilor Rob Consalvo would require diesel-fueled municipal vehicles to mix in biodiesel.

To counter rising sea levels, state Representative Marty Walsh envisions floating buildings and a series of locks and dams ringing the city, while Bill Walczak, a former health care executive, would preserve marshland to build buffer zones for flood protection.

Councilors Felix Arroyo and John Connolly want to boost the city’s recycling rate by making composting containers as common on curbs as recycling bins, while John Barros, executive director of the Dudley Street Neighborhood Initiative, wants to hire youths to plant thousands of trees around Boston.

In response to questions submitted by the Globe, nine of the 12 candidates running to be the city’s next mayor proposed a range of novel ideas about how to improve the city’s dismal recycling rate, realize ambitious goals to cut carbon emissions, and fight pollution, among other environmental issues that Boston will confront in coming years.